In broadband wireless communication systems such as 3GPP Long-Term Evolution (LTE) wireless networks the design of wireless mobile devices is a trade-off between performance and battery life. The receivers implemented in wireless mobile device provide adequate performance for typical radio frequency (RF) propagation conditions. However there are situations where RF performance is sub-optimal resulting in failures of the link between the wireless mobile device and the base station. There is always a tradeoff between link performance (being able to successfully decode the transmission from the base station) and power dissipation which directly corresponds to battery life. It is possible to choose very complex algorithms to process the signal that yield better link performance but also lead to higher power dissipation.
LTE systems employ Hybrid-ARQ (automatic repeat request) error control method in the receive path to improve the ability likelihood of the decoder to successfully decode in poor signal conditions. With HARQ, the wireless mobile device provides an acknowledgement (ACK) message if the received packet was successfully decoded or a negative-acknowledgement (NAK) if the message was not successfully decoded. The base station retransmits the packet if a NAK is received for a predetermined number of times before discarding the packet. Unless RF conditions improve from when a NAK was generated by the wireless mobile device and the next re-transmission, the likelihood of successfully decoding the retransmission is limited.
Similarly when performing a hand-off between base stations (or cells) the signal strength of adjacent cells can severely degrade link quality prior to handoff. In LTE the handoff between base stations is directed by the network resulting in potential periods where the signal strength of a serving base station degrades drastically as the signal strength of the adjacent base station increases prior to receiving a handoff message. Existing wireless mobile device designs rely on a single receiver design to address varying RF conditions and provide adequate power dissipation performance. The selection of a wireless mobile device receiver that fits the bulk of RF conditions limits the ability of the receiver to address sub-optimal RF conditions that occur frequently for short periods of time.
Therefore there is a need for improved state dependent advanced receiver processing in a receiver of wireless mobile devices.
It will be noted that throughout the appended drawings, like features are identified by like reference numerals.